Invasive placebos in research on peripheral nerve blocks: a follow-up study

Introduction: The Serious Harm and Morbidity "SHAM" grading system has previously been proposed to categorize the risks associated with the use of invasive placebos in peripheral nerve block research. SHAM grades range from 0 (no potential complications, eg, using standard analgesia techniques as a comparator) through to 4 (risk of major complications, eg, performing a sub-Tenon's block and injecting normal saline). A study in 2011 found that 52% of studies of peripheral nerve blocks had SHAM grades of 3 or more.

Methods: We repeated the original study by allocating SHAM grades to randomized controlled studies of peripheral nerve blocks published in English over a 22-month period. Documentation was made of the number of study participants, age, number of controls, body region, adverse events due to invasive placebos and any discussion regarding the ethics of using invasive placebos. We compared the proportion of studies with SHAM grades of 3 or more with the original study.

Results: In this current study, 114 studies fulfilled the inclusion criteria, 5 pediatric and 109 adult. The SHAM grade was ≥3 in 38 studies (33.3%), with 1494 patients in these control groups collectively. Several studies discussed their reasons for choosing a non-invasive placebo. No pediatric studies had a SHAM grade of ≥3.

Conclusions: The use of invasive placebos that may be associated with serious risks in peripheral nerve block research has decreased in contemporary peripheral nerve block research.